JP5259697B2 - Signal modulation method - Google Patents

Description

  The present invention relates to the field of communications, and more particularly to a signal modulation method based on a QPSK Spreading technique.

  The 3rd generation mobile communication system (IMT-2000) and its evolution system thoroughly solve the main adverse effects of the 1st and 2nd generation mobile communication systems, and at any time and any place within the global range, the mobile user All terminal users with facilities can complete any information mobile communication and transmission with any person in any manner with high quality. Compared to first and second generation mobile communication systems, IMT-2000 is an advanced mobile communication system. Currently, the standards applied to IMT-2000 are the time division-code division multiple access (TD-SCDMA) standard established by China, the code division multiple access (CDMA) 2000 standard established by the United States, and Europe. Includes the Wideband Code Division Multiple Access (WCDMA) standard. The CDMA 2000 standard is widely used in North America and many parts of the world.

  As the Internet and mobile communication technology continue to advance and the standard of living improves, mobile user equipment will be rapidly spread. In order to satisfy the demand for high-speed data services of terminal users with mobile user equipment, the CDMA 2000 standard was further developed and EV / DO and EV / DV, which are the evolution standards of CDMA 2000, were established. Both EV / DO and EV / DV are enhanced technologies based on CDMA2000 that can support higher-speed wireless packet data operations than CDMA2000. Among them, EV / DO refers to transmitting two tasks of voice and data on two independent carriers, respectively. EV / DV refers to transmitting voice and data tasks on the same carrier. It is to be. A mobile communication system based on EV / DO and EV / DV can provide abundant mobile multimedia services to terminal users.

  Based on EV / DO, we proposed further enhanced broadcast multicast service (abbreviated as EBCMCS) consultation, and the EBCMCS system based on EBCMCS consultation broadcast messages to mobile stations in all coverage areas of base stations Send.

  As shown in FIG. 1, the channel structure of the EBCMCS system in the prior art is orthogonal to a first unit 102 used for channel coding and a second unit 104 used for channel scrambling, interleaving and duplication. A third unit 106 used for amplitude (QAM) modulation and a fourth unit 108 used for orthogonal frequency division multiplexing (OFDM) modulation processing are included. Among them, the third unit 106 employs a 16 QAM modulation system. Specifically, the fourth unit 108 includes a module 1082 for inserting a protection interval and a pilot frequency, a QPSK frequency spreading module 1084, an inverse fast Fourier transform (IFFT) module 1086, and a cyclic prefix addition module 1088. ,including.

  Correspondingly, the processing flow of the signal input to the EBCMCS system is as follows: The signal input to the EBCMCS system is first channel coded by the first unit. The channel coding is 1/5 or 1/3 Turbo coding. Next, channel scrambling, interleaving, duplication, and slotting are performed on the coded signal by the second unit. Further, the third unit divides the slotted signal into two ways of I and Q by the 16QAM modulation method. Finally, the fourth unit performs OFDM modulation processing on each of the input I and Q 2-way signals. This ends the processing flow. Among them, the EBCMCS system adopts multi-carrier modulation as the OFDM modulation processing method, adopts the QPSK frequency spreading module in the fourth unit, and does not include the QPSK frequency spreading module and adopts the OFDM modulation processing method. Unlike the carrier modulation system, the signal peak-to-average power rate (abbreviated as PAPR) after the OFDM modulation processing of the multi-carrier modulation system is reduced.

  Specifically, the signal PAPR in a multi-carrier modulation system is usually obtained as follows. That is, in a multi-carrier modulation system that employs an OFDM modulation processing method, a sequence with a length N of an input signal sequence is

(N is the amount of OFDM sub-carrier). If the duration of the input signal X (n) is T, each corresponding input signal X (n) is assigned to one OFDM sub-carrier, that is, {f _n , n = 0, 1,..., N−1}. Modulated. In this case, the N OFDM subcarriers should be orthogonal, and

In Although,

It is. Finally, in Equation (1), the signal after OFDM modulation processing is shown as follows:

  Nyquist sampling is performed on the signal, and with equation (2), the acquired distributed signal can be expressed as:

  From Equation (1) and Equation (2), the resulting peak-to-average power ratio can be expressed as follows:

  Compared to a single carrier modulation system, a multi-carrier modulation system employs an OFDM modulation processing method, so that its output is a superposition of a plurality of subchannel signals. Therefore, when the phases of multiple subchannel signals match, the instantaneous output of the superimposed signal acquired is much larger than the average output of the subchannel signal, and generates a large signal PAPR. They made very high demands. If the linear range of the amplifier is not satisfied with the change of the subchannel signal, the subchannel signal is distorted and the orthogonality between each subchannel signal is destroyed by changing the frequency spectrum of the superimposed signal, Interfering with each other will degrade the performance of the multi-carrier modulation system.

  Since the EBCMCS system is also a multi-carrier modulation system that employs the OFDM modulation processing method, the conventional technology is used despite the fact that the PAPR of the signal after the OFDM modulation processing of the multi-carrier modulation system is reduced by increasing the QPSK frequency spreading module QPSK spread frequency modulation method in the EBCMCS system adopting the QPSK frequency spread module only performs 1-way QPSK spread frequency modulation on the signal input to the QPSK frequency spread module. The effect of reducing the PAPR of the signal by the frequency modulation method is not remarkable, and the demand for the linear range of the multi-carrier modulation system transmission output is high, which is disadvantageous for the design of the transmission output and also increases the cost of the transmission output Become.

  In view of one or several of the above problems, the present invention provides a modulation method that lowers the peak-to-average power ratio of a signal.

  In the signal modulation method according to the embodiment of the present invention, channel coding is performed on an input signal, and one of channel scrambling, interleaving, duplication, and slotting processing is performed on the channel-coded signal. A step of performing multiple processing, a step of dividing the processed signal into two parts of I and Q constituting the signal pair, and dividing the signal pair into one or more ways, and different frequency spreads for the signals of each way A sequence is used to perform quadrature phase shift keying (QPSK Spreading) and quadrature modulation to obtain the peak-to-average power ratio of the quadrature modulation of each way, and peak-to-average power Outputting a 1-way signal having a minimum ratio as an output signal.

Then, a frequency spreading sequence is generated by the following equation. That is, h (D) = D ¹⁷ + D ¹⁴ +1. In some cases, the signal pair is divided into M-way, and when the frequency spread sequence is s [k], k = 0, ..., 8N _FFT [i] -1, the frequency spread sequence used for each M-way signal Is

It is.

  And the signal pair is

, The 4-phase shift keying frequency spreading (QPSK Spreading) method adopted for the I part of the signal pair is

The four-phase shift keying frequency spreading (QPSK Spreading) method adopted for the Q part of the signal pair is

It is.

  And the I part of the signal pair that has undergone four-phase shift keying frequency spreading (QPSK Spreading)

And the Q portion of the signal pair that has undergone four-phase shift keying frequency spreading (QPSK Spreading)

It is. Among them, signal pairs subjected to four-phase shift keying frequency spreading (QPSK Spreading) are shown in a plurality of formats as follows.

  And

In this way, quadrature modulation is performed on a signal pair that has undergone four-phase shift keying (QPSK Spreading). Among them,

It is.

  And

In this manner, the peak-to-average power ratio of the signal pair after quadrature modulation is obtained. Among them, x (t) indicates a signal pair subjected to quadrature modulation. Selectively,

In this manner, the peak-to-average power ratio of the signal pair after quadrature modulation is obtained. Also,

To obtain the minimum peak-to-average power ratio. Among them, x (t) represents a signal pair subjected to quadrature modulation.

  In the present invention, the signal input to the QPSK frequency spread module is divided into one or more ways, and each way signal is subjected to QPSK spread frequency modulation. When performing QPSK spread frequency modulation, On the other hand, modulation is performed using different frequency spread sequences. The present invention performs QPSK spread frequency modulation for each way signal of 1 way or more, and adopts a different frequency spread sequence for each way signal, so that different signal PAPR can be obtained. , The smallest PAPR in the PAPR of all acquired signals can be selected. Therefore, the signal PAPR can be significantly reduced, and it is advantageous for the design of the transmission output, and the cost of the transmission output can be reduced.

The drawings described herein are for the purpose of deepening the understanding of the present invention, and constitute a part of the present application, and the embodiments shown in the present application and the description thereof are to interpret the present invention and unduly limit the present invention. Not what you want.
It is a figure which shows the structure of the channel structure of the EBCMCS system in a prior art. 4 is a flowchart illustrating an implementation of a QPSK spread frequency modulation scheme according to an embodiment of the present invention. It is a figure which shows the frequency-spread sequence generation system by the Example of this invention. The first way s ⁰ employed in the frequency spreading sequence of the invention embodiment is a view showing a frequency spreading sequence. It is a figure which compares and shows the effect which reduced signal PAPR with the method by the Example of this invention, and the QPSK spread frequency modulation method in a prior art.

  The core idea of the present invention is that the signal input to the QPSK frequency spread module is divided into M ways, and each way signal of the M way is subjected to QPSK spread frequency modulation and QPSK spread frequency modulation is performed. In other words, different frequency spread sequences are adopted for the signals of each way. The present invention performs QPSK spread frequency modulation on each way signal of the M way and adopts a different frequency spread sequence for each way signal, so that different signal PAPR can be obtained. It is possible to select the smallest signal PAPR among all the received signals PAPR.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

According to the signal modulation method of the embodiment of the present invention, the channel structure is based on the channel structure of the EBCMCS system shown in FIG. 1, but the main difference is that the QPSK spread frequency modulation method adopted for the QPSK frequency spread module is changed. That is. A signal modulation method according to an embodiment of the present invention includes the following steps:
Step 1: Channel coding is performed on the input signal of the first unit used for channel coding. Among them, channel coding is 1/5 or 1/3 Turbo coding.

  Step 2: Connected to the first unit and used for channel scrambling, interleaving and duplication, the second unit uses the channel scrambling, interleaving, Duplicate and slotting.

  Step 3: The third unit connected to the second unit and used for QAM modulation divides the slotted signal into I and Q two-way signals. The two-way signals are a pair; among them, the third unit employs a 16QAM modulation scheme and performs QAM modulation.

  Step 4: The fourth unit connected to the third unit and used for the OFDM modulation process divides the obtained I and Q signal pairs into one or more ways, and each frequency signal is spread differently. After the sequence is adopted and QPSK spread frequency modulation is performed to obtain all the signals PAPR, the smallest signal QPSK is selected as an output signal.

As shown in FIG. 2, step 4 includes the following steps:
S202: The module for inserting the protection interval and pilot frequency in the fourth unit outputs the received I and Q signal pair to the connected QPSK frequency spreading module.

  S204: The QPSK frequency spreading module divides the received I and Q signal pairs into M ways, adopts different frequency spreading sequences for each way signal, performs QPSK spreading frequency modulation, and performs QPSK spreading frequency modulation Output the I and Q signals of each way to the connected IFFT module.

  Among them, by EBCMCS consultation, the frequency spreading sequence adopted in step S204 can be generated according to equation (4):

  Equation (4) is a frequency spread sequence polynomial, also called the longest linear feedback shift register sequence, and is an m sequence. Fig. 3 is based on the EBCMCS discussion, and is a diagram that schematically shows the spread spectrum sequence generation method and does not completely show equation (4).

For example, if the initial value of the register is _{[1c 9 c 8 c 7 c} 6 c 5 c 4 c 3 c 2 c 1 c 0 x 5 x 4 x 3 x 2 x 1 x 0], as shown in FIG. 3 10 bits of c ₉ c ₈ c ₇ c ₆ c ₅ c ₄ c ₃ c ₂ c ₁ c ₀ are determined by the frequency spreading factor (FDSSeed, Frequency domain spreading seed), and x ₅ x ₄ x ₃ The 6 bits of x ₂ x ₁ x ₀ are determined by the system time. It is necessary to generate a frequency spreading sequence according to Equation (4) and map the generated frequency spreading sequence. A specific mapping method is to map a bit (bit) where the electric signal is 0 to +2 ^(−1/2) and a bit (bit) where the electric signal is 1 to −2 ^(−1/2) . Is mapping. Among them, in order to guarantee data synchronization, the numerical value in the register needs to be initialized at the start slot of the physical layer package of each transmission.

Correspondingly, if the frequency spread sequence is s [k] and k = 0, ..., 8N _FFT [i] -1, different frequency spread sequences to be adopted for the signals of each way in the M way The details are as follows:

Among them, N _FFT [i] is defined by EBCMCS consultation. This parameter defines the conversion index to be used for IFFT module quadrature modulation.

Among them, the specific acquisition method of the frequency spread sequence of the first way s ⁰ adopted in the frequency spread sequence is as shown in FIG. 4, and the frequency spread sequence used is that specified in the EBCMCS consultation. Similarly, in short, it is a frequency spreading sequence that can participate in QPSK frequency spreading. That is, the length of the m-sequence generated according to the equation (4) is 2 ¹⁷ −1, and the package of each physical layer is divided into some slots (for example, two slots) according to the EBCMCS consultation. There are 2048 chips in each slot. In consideration of backward compatibility, the number of data that each slot can store is 1600 chips. The number of chips in the frequency spreading sequence that can participate in QPSK frequency spreading in one slot (slot) should be 1600, but since it is necessary to add a cyclic prefix to OFDM, The number of chips of a frequency spreading sequence for performing QPSK frequency spreading in a slot is 4 × N _FFT [i]. Since the total number of chips in the frequency spread sequence is 1600, N _FFT [i] must be less than or equal to 400, and usually the numbers are 320, 360, and 384.

When QPSK frequency spreading is performed by the signal modulation method according to the embodiment of the present invention, QPSK frequency spreading is performed by the spreading frequency modulation method shown in Equation (6) and Equation (7). According to Equation (6) and Equation (7), it is necessary to use different frequency spreading sequences for I-way and Q-way, and the one used in Equation (6) and Equation (7) is s [ 2k] and s [2k + 1]. When performing QPSK frequency spreading in each slot, the number of chips of the frequency spreading sequence adopted is 8 × N _FFT [i]. Correspondingly, the frequency spread sequence which is the minimum signal PAPR is selected from N × N _FFT [i] frequency spread sequences and transmitted, and the number of the selected frequency spread sequence is transmitted to the receiver. .

  S206: IFFT module acquires I and Q signals of each way that are QPSK spread frequency modulated, performs quadrature modulation on the acquired I and Q signals of each way, and signals of M way I and Q signals After acquiring the PAPR, the one-way signal having the smallest signal PAPR is selected as an output signal and output to the connected module with the cyclic prefix.

For example, the I and Q signal pair received in step S202 is C " _{I / Q} [i] [k], and

The QPSK spread frequency modulation method according to an embodiment of the present invention includes the following steps:
S202: The module for inserting the protection interval and the pilot frequency in the fourth unit outputs the received I, Q signal pair C " _{I / Q} [i] [k] to the connected QPSK frequency spreading module.

  S204: The QPSK frequency spreading module divides the received signal into M ways, and adopts a different frequency spreading sequence for each way signal to perform QPSK spreading frequency modulation.

At this time, QPSK spread frequency modulation is performed on the signal of each way, and the obtained I and Q signal pair after QPSK spread frequency modulation is u _{I / Q} [i] [k] and i = 0, …, N _spp −1, k = 0,…, 4N _FFT [i] −1, where N _FFT [i] and N _spp are defined by the EBCMCS consultation. Then, the adopted QPSK spread frequency modulation scheme is specifically as follows:

  According to Equation (6) and Equation (7), QPSK spread frequency modulation is performed on each way signal of the M way, and the signal of each way after QPSK spread frequency modulation is output to the connected IFFT module.

  Among them, when adopting a different frequency spread sequence obtained according to Equation (5) for each way signal in the M way, correspondingly, for each way signal in the M way, Equation (6 ) And Equation (7), and after performing QPSK spread frequency modulation, I and Q signals of each way after QPSK spread frequency modulation are acquired. The details are as follows:

  Among them, the I and Q signals of each way subjected to QPSK spread frequency modulation can be shown in a plurality of formats as follows.

S206: The IFFT module acquires I and Q signals of each way after QPSK spread frequency modulation, and performs orthogonal modulation on the acquired I and Q signals of each way. Among them, when the acquired signal after orthogonal modulation is v ^m [i] [k ′], details of the orthogonal modulation method to be employed are as follows.

  Here, a signal after quadrature modulation is indicated by x (t). Correspondingly, the signal PAPR after quadrature modulation of each way is calculated according to equation (3). The signal PAPR is the ratio of the maximum signal output to the average signal output for all signals after quadrature modulation.

  Finally, after all the signals PAPR are acquired, the minimum signal PAPR is output as an output signal and output to the connected cyclic prefix added module.

  Among them, in the QPSK spread frequency modulation system, the multiplication operation on the signal is equivalent to performing interference on the phase of the signal and does not affect the average output of the signal. The calculation of the signal PAPR after the quadrature modulation of the way is

Can be simplified. That is, the equation for calculating the signal PAPR can be simplified to calculate the maximum output of all signals after quadrature modulation. Among them, when the signal after quadrature modulation is indicated by x (t), the details of the equation for selecting the signal PAPR are as follows.

Since there is no way to know the selected spread spectrum sequence at the receiver, it is necessary to transmit the selected information as sideband information to the receiver so as to perform modulation, so the data amount of the transmitted signal is log ₂ (M) Must be a bit. FIG. 5 is a diagram comparing the effect of lowering the signal PAPR with the method according to the embodiment of the present invention and the conventional QPSK spread frequency modulation method. In FIG. 5, the horizontal axis is the signal PAPR, and the vertical axis is the function value corresponding to the complementary cumulative density function (abbreviated as CCDF) of the signal PAPR. The effect diagram shown in FIG. 5 is a curve diagram showing the function distribution of the complementary cumulative distribution function. From the curve diagram, it is possible to intuitively obtain a contrast of the signal PAPR acquired by different frequency spreading methods. FIG. 5 shows the function distribution curve of the complementary cumulative distribution function corresponding to the acquired signal PAPR when the QPSK frequency spreading method of the embodiment of the present invention is adopted and M = 4, M = 8 and M = 16. Illustration is included.

  In FIG. 5, the symbol “rice” indicates a signal PAPR obtained after QPSK frequency spreading by the QPSK frequency spreading method in the prior art. All other symbols indicate the signal PAPR obtained after QPSK frequency spreading by the QPSK frequency spreading method in the embodiment of the present invention. Among them, the signal PAPR obtained after QPSK frequency spreading when the curve marked with a circular symbol is M = 16, the curve marked with a square symbol is M = 8, and the curve marked with a diamond symbol is M = 4 Indicates.

  As can be seen intuitively from FIG. 5, when M = 4, M = 8 and M = 16, the method according to the embodiment of the present invention can suppress the signal PAPR better than the method in the prior art, and the signal PAPR Is significantly reduced.

  The foregoing is merely a preferred embodiment of the present invention and does not unduly limit the present invention. For those skilled in the art, various modifications can be made without departing from the spirit of the present invention. Any modification, equivalent replacement, or improvement made should be included in the protection scope of the present invention as long as it is within the scope of the object and principle of the present invention.

Claims (7)

Performing channel coding on the input signal and performing one or more processes in channel scrambling, interleaving, duplication, slotting on the channel coded signal;
Dividing the processed signal into two parts, I and Q, constituting one signal pair;
The signal pair is divided into one or more ways, and different frequency spreading sequences are used for the signals of each way to perform quadrature phase shift keying (QPSK Spreading) and quadrature modulation to perform quadrature modulation. Obtaining a peak-to-average power ratio for each way signal;
A step of peak-to-average power ratio to output a minimum of 1 way signal as an output signal, only including,
The frequency spreading sequence is generated according to the equation h (D) = D ¹⁷ + D ¹⁴ +1,
When the signal pair is divided into M-way and the frequency spread sequence is s [k], k = 0,..., 8NFFT [i] -1, the frequency spread sequence used for each of the M-way signals Is

Signal modulation wherein the at. In claim 1 ,
The signal pair is

When
The four phase shift keying frequency spreading (QPSK Spreading) method employed for the I part of the signal pair is:

And, the four phase shift keying frequency spreading (QPSK Spreading) method adopted for the Q part in the signal pair is:

A signal modulation method characterized by the above. In claim 2 ,
The I part of a signal pair that has undergone four phase shift keying frequency spreading (QPSK Spreading)

And the Q portion of the signal pair that has undergone four-phase shift keying frequency spreading (QPSK Spreading)

A signal modulation method characterized by the above. In claim 3 ,
The signal pair subjected to the four phase shift keying frequency spreading (QPSK Spreading) in a plurality of formats,

A signal modulation method characterized by the following. In claim 3 or 4 ,
For the signal pair subjected to the four phase shift keying frequency spreading (QPSK Spreading),

A signal modulation method characterized by performing quadrature modulation in the manner described above. In claim 5 ,
The peak-to-average power ratio of a signal pair that has undergone quadrature modulation,

A signal modulation method obtained by the method of The peak-to-average power ratio of the signal pair subjected to quadrature modulation according to claim 5 ,

To obtain the minimum peak-to-average power ratio,

The signal modulation method characterized by acquiring by the system.

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